You can open OST files in Outlook—or convert OST, Outlook PST, and Outlook NST files into various formats—by using the
eSoftTools OST to PST Converter software. This tool comes packed with features and supports all Outlook mailbox items, including emails, contacts, calendars, notes, and tasks. You can also try out the software using a free demo version, which is compatible with any Windows system.
Read More:- Open an OST file to Outlook